One of the world's most common fatal diseases is vascular disease, in particular heart infarct. This is caused by diseases of the coronary arteries (Arteriosclerosis). Deposits (arteriosclerotic plaque) result in a ‘blockage’ in the coronary arteries.
If the coronary angiography shows serious narrowing (Stenosis) in the coronary arteries, which cause angina pectoris, restrict a person's performance and/or pose a threat to the life of the patient, then a PTCA (percutaneous transiluminal coronary angioplasty) is nowadays carried out in the majority of cases. During this the constrictions in the coronary arteries are widened using a so-called balloon catheter.
Clinical studies have shown that with many patients, this method results in restenosis, sometimes up to 50% of patients show restenosis. The use of stents positioned in the widened constrictions can reduce the restenosis rate by up to 25%.
Endovascular brachytherapy can further reduce restenosis, the method was first licensed in 2000 by the FDA (Food and Drug Administration) for a beta and a gamma-radiator. The advance of the causal arteriosclerosis and the response of the vessel wall to the PCTA-induced trauma are causes for post-interventional restenosis. The stent implantation prevents a structural vessel alteration by means of the mechanical restoring force of the stent, but nevertheless stimulates the neointima hyperplasia. In contrast, after a single PTCA the structural vessel alteration predominates during the onset of restenosis.
Clinical studies have shown that the endovascular radiation reduces the restenosis. The mechanisms have still not be fully clarified, nevertheless different models are discussed, e.g. cell death, cell inactivation, hindrance in the cell migration, suppression of the structural vessel alteration and blockage of the extra cellular matrix synthesis.
The radioactivity can either be applied by means of catheter-based radioactive wires or seeds, or administered as radioactive fluids directly by means of a PTCA balloon. Previous experience has shown that the concept of the radioactively loaded stents unfortunately shows a high restenosis rate. The wire-based systems stand out as the most favorable solution. With wire-based systems, the radiation source is applied to the tip of a wire which is then manually moved into the target position by means of a mechanical after-loading device. One problem of this technique is the possibly eccentric position of the wire in the vessel volume. This results in an overdosage on the vessel wall side near to the wire and an underdosage on the vessel wall side away from the wire.
For centering of the radioactive wire in the vessel lumen segmented and helical balloons are fitted to the applicator around the wire, which should guarantee an improved homogeneity of the radiation dose. [Wohlgemut W A, Bohndorf K Endovasculäre Brachytherapie in der Restenoseprophylaxe nach Angioplastie und Stentimplantation, Fortsch. Röntgenstr. 2003; 175; 246-252]. (Endovascular Brachytherapy in the restonosis prophylax after angioplasty and stent implantation).